Process of forming a photoactive layer of a perovskite photoactive device

Abstract

A process of forming a photoactive layer of a planar perovskite photoactive device comprising: applying at least one layer of a first precursor solution to a substrate to form a first precursor coating on at least one surface of the substrate, the first precursor solution comprising MX 2 and AX dissolved in a first coating solvent, wherein the molar ratio of MX 2 :AX=1:n with 0<n<1; and applying a second precursor solution to the first precursor coating to convert the first precursor coating to a perovskite layer AMX 3 , the second precursor solution comprising AX dissolved in a second coating solvent, the first precursor solution reacting with the second precursor solution to form a perovskite layer AMX 3 on the substrate, wherein A comprises an ammonium group or other nitrogen containing organic cation, M is selected from Pb, Sn, Ge, Ca, Sr, Cd, Cu, Ni, Mn, Co, Zn, Fe, Mg, Ba, Si, Ti, Bi, or In, X is selected from at least one of F, Cl, Br or I.

The invention claimed is: 
     
       1. A process of forming a photoactive layer of a flexible planar perovskite photoactive device comprising:
 applying at least one layer of a first precursor solution to a flexible planar substrate to form a first precursor coating on at least one surface of the substrate, the first precursor solution comprising MX2 and AX dissolved in a first coating solvent, wherein the molar ratio of MX2:AX=1:n with 0<n<1; and 
 applying a second precursor solution to the first precursor coating to convert the first precursor coating to a perovskite layer AMX3, the second precursor solution comprising AX dissolved in a second coating solvent, the first precursor solution reacting with the second precursor solution to form a perovskite layer AMX3 on the substrate, thereby forming a photoactive layer of the flexible planar perovskite photoactive device, 
 wherein A comprises an ammonium group or other nitrogen containing organic cation, M is selected from Pb, Sn, Ge, Ca, Sr, Cd, Cu, Ni, Mn, Co, Zn, Fe, Mg, Ba, Si, Ti, Bi, or In, X is selected from at least one of F, Cl, Br or I. 
 
     
     
       2. The process according to  claim 1 , wherein the molar ratio of MX 2 :AX=1:n with 0<n≤0.5. 
     
     
       3. The process according to  claim 1 , wherein the process further involves the step of:
 drying the first precursor coating prior to applying the second precursor solution. 
 
     
     
       4. The process according to  claim 1 , wherein the process further involves the step of:
 subjecting the substrate with first precursor coating to a solvent vapour soaking process before applying the second precursor solution to the first precursor coating. 
 
     
     
       5. The process according to  claim 4 , wherein the substrate is subjected to the solvent vapour soaking process immediately after the first precursor solution is applied to the substrate. 
     
     
       6. The process according to  claim 1 , wherein MX 2  and AX are soluble in the first coating solvent, AX is soluble in the second coating solvent, and MX 2  has a low to zero solubility in the second coating solvent. 
     
     
       7. The process according to  claim 1 , wherein the first coating solvent comprises DMF, DMSO, Y-butyrolactone, acetone, acetyl acetone, ethyl acetoacetate, NMP, DMAC, THF or combinations thereof. 
     
     
       8. The process according to  claim 1 , wherein the second coating solvent is at least one of including isopropanol, n-butanol, isobutanol, ethanol, methanol, acetic acid, ethylene glycol, propylene glycol, glycerol, allyl alcohol, propagyl alcohol, inositol or combinations thereof. 
     
     
       9. The process according to  claim 1 , wherein A in AX comprises an organic cation having the formula (R 1 R 2 R 3 R 4 N), wherein:
 R 1  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; 
 R 2  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; 
 R 3  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; and 
 R 4  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl. 
 
     
     
       10. The process according to  claim 1 , wherein A in AX comprises an organic cation having the formula (R 5 R 6 N═CH—NR 7 R 8 ), and wherein:
 R 5  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; 
 R 6  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; 
 R 7  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl; and 
 R 8  is hydrogen, unsubstituted or substituted C1-C20 alkyl, or unsubstituted or substituted aryl. 
 
     
     
       11. The process according to  claim 9 , wherein AX is selected from the group consisting of CH 3 NH 3 X and HC(NH 2 ) 2 X, and wherein X is selected from at least one of F, Cl, Br or I. 
     
     
       12. The process according to  claim 1 , wherein the perovskite layer comprises an organo-metal halide perovskite. 
     
     
       13. The process according to  claim 12 , wherein the perovskite layer comprises at least one of CH 3 NH 3 MX 3  or HC(NH 2 ) 2 MX 3 , in which, M is selected from Pb, Sn, Tl, Bi, or In; and X is selected from at least one of F, Cl, Br or I. 
     
     
       14. The process according to  claim 1 , wherein the second precursor solution comprises from 5 to 75 wt % AX. 
     
     
       15. The process according to  claim 1 , wherein the substrate comprises at least one of a polymer, metal, ceramic or glass. 
     
     
       16. The process according to  claim 1 , wherein the substrate includes one or more layers or coatings selected from at least one of:
 at least one coating of a transparent conductive oxide (TCO); 
 at least one hole transporting layer comprising an organic or inorganic semiconductor; or 
 at least one electron transporting layer comprising an organic or inorganic conductor. 
 
     
     
       17. The process according to  claim 1 , wherein the first precursor coating has a dry layer thickness from 100 nm to 600 nm. 
     
     
       18. The process according to  claim 1 , wherein at least one of the first perovskite precursor solution or the second precursor solution further comprises a perovskite crystallisation retardant comprising a polymer additive which is soluble in the respective first coating solvent or second coating solvent. 
     
     
       19. The process according to  claim 18 , wherein the polymer additive is selected from the group consisting of poly vinyl alcohol, poly vinyl acetate (PVAc), ABS, poly amides, poly acrylics, poly imide, poly acrylonitrile, poly butyl methacrylate, poly butadiene, poly carboxy methyl cellulose, poly ethers, poly ethylene acrylates, poly glycols, poly isocyanates, poly methacrylates, poly vinyl butyral, poly vinyl fluoride, poly vinyl methyl ethers, poly amines, polyethylene oxide, polyethylene glycol Poly(2-ethyl-2-oxazoline) and combinations thereof. 
     
     
       20. The process according to  claim 1 , wherein AX from the first precursor solution is incorporated into the final perovskite layer AMX 3 .